Introduce HostID and de-couple Extensions from "script injection System" [browser side]

extensions/renderer/user_script_set.cc

Index: extensions/renderer/user_script_set.cc
diff --git a/extensions/renderer/user_script_set.cc b/extensions/renderer/user_script_set.cc
index e95843d392880bebd48ce1b26bdfebce5b903951..416855583e1136ae7dbfdc3983acff2ee5a08e22 100644
--- a/extensions/renderer/user_script_set.cc
+++ b/extensions/renderer/user_script_set.cc
@@ -53,8 +53,8 @@ void UserScriptSet::GetActiveExtensionIds(
   for (ScopedVector<UserScript>::const_iterator iter = scripts_.begin();
        iter != scripts_.end();
        ++iter) {
-    DCHECK(!(*iter)->extension_id().empty());
-    ids->insert((*iter)->extension_id());
+    DCHECK(!(*iter)->GetExtensionID().empty());
+    ids->insert((*iter)->GetExtensionID());
   }
 }
 
@@ -67,7 +67,8 @@ void UserScriptSet::GetInjections(
   for (ScopedVector<UserScript>::const_iterator iter = scripts_.begin();
        iter != scripts_.end();
        ++iter) {
-    const Extension* extension = extensions_->GetByID((*iter)->extension_id());
+    const Extension* extension =
+        extensions_->GetByID((*iter)->GetExtensionID());
     if (!extension)
       continue;
     scoped_ptr<ScriptInjection> injection = GetInjectionForScript(